Acute reperfusion strategies for ST-segment elevation myocardial infarction.

The overall aim of reperfusion therapy for patients presenting with an ST-segment elevation myocardial infarction (STEMI) is to restore normal blood flow in the infarct-related artery as rapidly and completely as possible, and thus myocardial perfusion. This can be achieved by the administration of thrombolytic therapy (either pre-hospital or in hospital) or by primary percutaneous coronary intervention (PPCI). Guidelines suggest that thrombolytic therapy should be administered within a door to needle time (or medical contact to needle time) of ,30 min and a door to balloon time of ,90 min for PPCI. Eagle et al. report the trends in acute reperfusion therapy from the GRACE registry for patients presenting with a STEMI from 1999 to 2006. There was an increase in primary PCI (from 15 to 44%) and a decline in thrombolytic therapy (from 41 to 16%). In addition, 32–40% of patients received no reperfusion therapy and a significant number of patients received reperfusion outside of the time guidelines (52% door to needle time .30 min; 42% door to balloon time .90 min). The ACC/AHA guidelines for the management of patients presenting with a STEMI indicate that the reperfusion strategy should be based on the time from onset of symptoms, patient-based risk factors, and the ability of the centre to provide rapid and effective PPCI. Although PPCI achieves higher TIMI III flow rates compared with thrombolytic therapy, door to balloon times are often longer in clinical studies, resulting in delayed reperfusion. There is evidence from randomized control trials that lower mortality rates, reinfarction, intracranial haemorrhage, and stroke occur in patients undergoing PPCI within the recommended guidelines compared with thrombolytic therapy. Additionally, in patients at increased risk of bleeding or in cardiogenic shock, PPCI is superior. However, if thrombolytic therapy can be given within 60 min of presentation, this may be more advantageous than delaying for PPCI. The ACC/AHA guidelines state that STEMI patients presenting within 90 min of first medical contact to a unit without the facilities for prompt PPCI should receive thrombolytic therapy. Several studies have shown that in patients who present very early, i.e. within 2–3 h after onset of symptoms, there is no difference in in-hospital or 30 day mortality between patients who receive thrombolytic therapy or PPCI, with a trend in favour of thrombolytic therapy. – 8 Furthermore, the ASSENT-3 study (Assessment of the Safety and Efficacy of a New Thrombolytic Regimen) reported that if patients received very rapid thrombolytic therapy, the frequency of aborted myocardial infarction [defined as maximal creatine kinase 2 times the upper limit of normal with typical evolutionary changes on the electrocardiogram (ECG)] was 13.3%. The majority of aborted myocardial infarctions occurred within the first hour from symptom onset, with a sharp reduction in incidence after 3 h. In the study by Eagle et al., the pre-hospital delay was unchanged from 1999 to 2006 (median 120–133 min). In order to have a significant impact on reducing reperfusion times this issue needs to be addressed. In a comparison of pre-hospital thrombolytic therapy with PPCI in the CAPTIM study (Comparison of Angioplasty and Prehospital Thrombolysis in Acute Myocardial Infarction), the time to treatment for patients receiving pre-hospital thrombolytic therapy was 130 min compared with 190 min for those undergoing PPCI. This resulted in a 30 day mortality rate of 3.8% in the pre-hospital thrombolytic therapy group vs. 4.8% in the PPCI group. It is therefore fundamental that paramedics are trained in recording and analysing ECGs with facilities to transmit to a cardiology centre for interpretation and immediate advice. The decision can then be made pre-hospital to administer thrombolytic therapy or not. In the Vienna Ambulance Service, physicians diagnosed and triaged patients with acute STEMI to the fastest available reperfusion strategy for those with short duration (2–3 h) from symptom onset. The results from this study showed an increase in patients receiving reperfusion therapy from 66 to 86.6%, resulting in a reduction in in-hospital mortality from 16 to 9.5%, with a trend in favour of thrombolytic therapy within the first 2 h of treatment. If patients present to a hospital without PPCI facilities it may also be more favourable to administer